An outdoor electric power terminal filled with silicon oil may be applied to a high voltage cable of, for example, 170 kV. However, there is a risk that the silicon oil may leak out of the outdoor electric power terminal and cause a serious power failure. Furthermore, the outdoor electric power terminal is often mounted high above the ground. Therefore, it is difficult to find the leaked silicon oil in time.
Known silicon oil sensors generally include a conductive layer directly formed by conductive particles or a porous material, for example, polytetrafluoroethylene (PTEE) filled by conductive particles. When the silicon oil flows to the conductive layer of the silicon oil sensor, the conductive particles directly contact the silicon oil and are wrapped by the silicon oil, resulting in changes of the electric resistance of the conductive layer. Thereby, it is possible to detect whether the silicon oil leaked of the outdoor electric power terminal based on the change of the electric resistance of the conductive layer of the silicon oil sensor. However, in the known silicon oil sensor, when the conductive particles are wrapped by the leaked silicon oil, the change of the electric resistance of the conductive layer is very slow and not significant, that is, this known silicon oil sensor has poor detection sensitivity and cannot detect the leaked silicon oil in time. As a result, it cannot reliably prevent the power failure due to the leaked silicon oil.
In order to overcome the disadvantages of the above known silicon oil sensor, Japanese Patent Document No.JP1265138A discloses a known fiber sensor for the silicon oil. The known fiber sensor includes a fiber core fixed on a surface of a plastic body. Once the silicon oil is dropped onto the fiber core, the fiber sensor can determine that the silicon oil is leaked out of the electric power terminal. However, in the known fiber sensor, the known fiber sensor is formed a plastic body by pouring polymer material on the fiber and polishing the plastic body until the fiber core of the fiber is exposed. As a result, the process of manufacture of the fiber sensor is very complicated and difficult. Additionally, the size of the fiber is very small and cannot detect a large area and, therefore, it needs an additional funnel to collect the leaked silicon oil within the large area. Furthermore, the known fiber sensor is also affected by rain water or other liquid like the silicon oil. As a result, it may mistake the rain water as the leaked silicon oil when it is used in the outdoor environment.